How to Find All Duplicate Characters in String in Python

Submitted by razormist on Friday, May 29, 2026 - 23:21.

In this tutorial, we will learn how to program "How to Find All Duplicate Characters in String in Python". The objective is to find all the duplicate characters in a string. This tutorial will guide you step by step through the process of finding duplicate characters. By the end of this tutorial, you will have a solid understanding of how to implement this solution effectively in Python, helping you strengthen your problem-solving abilities and improve your coding skills.

This topic is straightforward and easy to understand. By following the instructions provided, you will be able to complete it with ease. The program will guide you step by step through the process of finding all duplicate characters in a string. So, let’s dive into the coding process!

Getting Started:

First you will have to download & install the Python IDLE's, here's the link for the Integrated Development And Learning Environment for Python https://www.python.org/downloads/.

Creating Main Function

This is the main function of the application. The following code will display a simple GUI in terminal console that will display program. To do this, simply copy and paste these blocks of code into the IDLE text editor.

from collections import Counter
 
# MAIN LOOP
while True:
    print("\n============= Find All Duplicate Characters in String =============\n")
 
    # Input string
    s = input("Enter a string: ").strip()
 
    if not s:
        print("Input cannot be empty.")
        continue
 
    # Count character frequencies
    d = Counter(s)
 
    # Find duplicate characters
    res = [char for char, cnt in d.items() if cnt > 1]
 
    print("\nDuplicate characters:")
    print(res)
 
    # Try Again Option
    opt = input("\nDo you want to try again? (yes/no): ").strip().lower()
 
    if opt == 'no':
        print("Exiting program...")
        break
    elif opt != 'yes':
        print("Invalid choice. Exiting program...")
        break

This Python program finds duplicate characters in a string using the `Counter` class from the `collections` module. It takes a user-input string, counts the frequency of each character, and then identifies characters that appear more than once. The program displays the list of duplicate characters and runs in an interactive loop, allowing users to repeat the process or exit with input validation included.

Output:

There you have it we successfully created How to Find All Duplicate Characters in String in Python. I hope that this simple tutorial help you to what you are looking for. For more updates and tutorials just kindly visit this site. Enjoy Coding!

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